1 Answer
1

Not much -- 220 film is twice as long as 120 film, so to put it on the same roller, they leave the paper backing off of the exposable film (or, rarely, use a much thinner protective backing). That means that your camera (or back) needs to have a pressure plate that can adjust to the reduced thickness in order to flatten the film properly, and that you can't use a camera or back that uses a window onto the back of the film to show the exposure number (a lot of very old cameras had a red-filtered window -- about twice the strength of a #25 -- that you could directly view the paper backing through, and film usually had frame numbers printed on the paper for 6x9 and 6x6).

[EDIT - ADDED] I should note that there is plenty of paper at both ends of the 220 roll so that loading and unloading film in the usual manner is as safe as it is for 120.